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Biomedical subjects

R J Minns

Publications and source records attributed to R J Minns.

At least 37 records · Page 2Linked to original sources
PubMed1987

Soft tissue augmentation as a method of reducing the liability to pressure sores in spinal injured patients.

The development of a procedure designed to reduce the liability to pressure sores over bony prominences is described. This employs the properties of a particular type of carbon fibre pad implanted surgically over the bony prominence. The mechanical response of the pad to loading has been examined. The host tissue response to the pad involves penetration of the interstices between the carbon fibres with organised fibrous tissue. The host-tissue--carbon fibre pad complex has been found to be highly vascular. An 'ischiobarograph' has been developed and used in order to evaluate the alteration in pressure profile produced by the presence of the implanted prosthesis (the patient being in a sitting position).

Animals↗
PubMed1986

Biomechanical testing of an anatomically contoured fixation plate for the tibia.

Simple bending and torsion and quasi-static physiological loading tests on two commonly used plating designs for internal fixation of the tibia were conducted and compared with a new design of anatomically shaped fixation plate. These simple static tests indicate that the new contoured plating system is mechanically more rigid under these test conditions than the conventional plating methods.

Biomechanical Phenomena↗
PubMed1985

The mechanics of skull traction calipers.

The relationship between the torque applied to the loading screw and the load required to pull off Cone's type of skull traction caliper was established on cadavers. It was found that at a torque of 0.7 Newton metres (Nm), which corresponds to a compressive force of 13 lb (58 N) on the skull, the caliper became detached at the maximum traction load of 60 lb, but still held during this traction load at compressive forces above 18 lb (80 N). Clinically, an instrumented load cell was incorporated into one of the fixing pins on a skull traction caliper and it was found that the compressive load fell on average by 15 per cent over a period of 21 days of traction. Taking into account this fall in load with time and the limiting torque for pull-out with a traction force of 60 lb (265 N) it is suggested, for complete clinical safety, that a compressive load of 20 lb (88 N) obtained at a torque of 0.85 Nm should be applied to the loading screw of a Cone's type of caliper. Using these values in a loading analysis of the securing pins, suggestions are made as to the ideal design of skull traction calipers and the shortcomings of various designs of existing calipers are discussed, in particular the pins' lengths, compressive load and the pins' placement.

Adult↗
PubMed1985

Tools for high tibial wedge osteotomy.

Surgical instruments are described which have been developed for use in high tibial wedge osteotomy. This operation is a treatment for degenerative arthritis of the knee in which one compartment of the joint is predominantly affected resulting in a deformity. Realignment of the bones alters the load distribution on the joint which can relieve pain. Tools have been designed to facilitate the removal of a wedge of bone cut at a precise angle calculated from load bearing radiographs. The tools are a marker pin guide and a saw guide; their use has resulted in accurate bone realignment confirmed by postoperative radiographs.

Biomedical Engineering↗
PubMed1985

Torque pull-out load characteristics of skull traction calipers of 'ice tong' type (with particular reference to the cone type of caliper). Technical note.

The relationship between the applied torque and the load required to pull off the calipers was established on cadavers. Torques of 0.7, 0.8 and 0.9 Newton-metres were applied to a specially adapted skull traction caliper whilst attached to the skull in the normal position when used clinically, and loads were applied in steps of 2 lb up to a maximum of 60 lb. It was found that at a torque of 0.7 Newton-metres, the caliper became detached at the maximum load, but still held during traction at torques above this value. Taking into account the fall in load with time that may occur clinically and the limiting torque for pull-out with a traction load of 60 lb, it is suggested for complete clinical safety that a torque of 0.9 Newton-metres should be applied. An open-ended torque release spanner was set for 0.9 Newton-metres for clinical use such that the compressive load is sufficient to prevent pull-out even in the unlikely event of 60 lb being applied for up to 21 days.

Humans↗
PubMed1984

Physical properties of cross-linked polyethylene foam (Plastazote) under clinical conditions.

Cross-linked polyethylene foam (Plastazote) has been used in the management of painful foot disorders occurring in a number of disease processes. A series of mechanical tests have been performed under varying clinically encountered conditions to show a relationship between the deformation of the material and the load applied to it. This has allowed the development of a method of assessment of the footprint impressed in a weight-bearing insole, and may help to clarify the observed results of treatment.

Biomechanical Phenomena↗
PubMed1984

Underseat pressure distribution in the sitting spinal injury patient.

A device has been developed that can display underseat pressure distributions during sitting. We have found this device to be particularly useful in monitoring the effect of pressure sore surgery on the underseat pressure patterns, in the design of pressure-relieving cushions, and as a device to enable spinal injury staff to locate areas of high pressure at which tissue breakdown (pressure sores) may occur.

Adolescent↗
PubMed1984

Plantar pressures and gait parameters: a study of foot shape and limb rotations in children.

The most frequent referral diagnosis of childhood to an orthopaedic department is a limb rotational anomaly which manifests itself as either an abnormality of gait or flatfeet. The child is usually asymptomatic, the anxiety being generated in the minds of the parents. One hundred normal children were studied using a Pedobarograph to assess underfoot pressures, and a simple walkway to measure dynamic gait parameters. The results have been correlated with age, and the trends suggest that the pedobarograms may be of use in the prognostication of lower limb rotations. The methods, which are totally noninvasive and can be carried out in the clinic, have the added advantage of reassuring parents that "something is being done."

Adolescent↗
PubMed1983

Failure of one design of surface replacement knee arthroplasty due to loosening deformation and wear of the plastic femoral component.

Twenty four knee prosthesis femoral and tibial components of the 'load angle inlay' design, removed for loosening and pain were examined in the scanning electron microscope, light microscope, and volume loss measured using a simple gauge. In all cases the deformation of the plastic (femoral) component was seen both by increase in the curvature of the inner surface and wear usually on the edge of the bearing surface. Two pairs were subluxed prior to removal from the patient and these not only produced gross deformation of the plastic components, but maximum volume loss of the components examined; the knees exhibited gross instability. The tibial (metal) components stood up remarkably well in all cases, both in wear and deformation which was minimal but sinking and rotation of the plateau did occur for the most part on the external side. Scratch patterns seen on the tibial components were clearly seen and gave an indication of the direction and amount of sliding between the components; in some cases these scratch lines were in more than one direction probably indicative of loosening and instability. Short deep scratches were usually indicative of bone and/or cement particles embedded in the plastic components, abrasive wear was seen on 92 per cent of the femoral components, and cracks were seen on two-thirds, usually parallel and close to the sides.

Adult↗
PubMed1983

The role of calcium in the mechanical behaviour of bone.

Plugs of fresh post mortem human patellar subchondral bone were soaked for three weeks in an organic solvent (ethanol) which contained a chelating agent (EDTA). This technique selectively removes the calcified inorganic component without disrupting the structure of the remaining bone matrix. These plugs, together with untreated plugs as controls, were treated in unconfined compression at a fixed strain rate and allowed to relax to evaluate the contribution made by the calcium component to the physical and time-dependent properties of subchondral bone.

Adolescent↗
PubMed1982

Mechanical properties of traumatized rat tendo-achilles and the effect of an anti-inflammatory drug on the repair properties.

This paper reports on the effect of orally administered flurbiprofen, a potent inhibitor of prostaglandin synthesis (cyclo oxygenase inhibitor), on the mechanical properties of traumatized rat tendo-achilles to see if the F2 alpha prostaglandin was affected and hence the repair process. The drug (1 mg) was administered daily for 7 days to 18 rats whose tendo-achilles were traumatized by crimping using a predetermined force (50 N) applied for 10s. Eighteen sham control rats were identically traumatized and given daily the same volume of liquid (water) not containing the drug. Forty non-traumatized, untreated rats were examined as controls. In vitro studies showed that there was no significant difference in the stress--strain and relaxation characteristics between the three groups and no histological differences were observed.

Achilles Tendon↗
PubMed1982

A conductive rubber footswitch design for gait analysis.

The performance of a footswitch which uses conductive rubber modules in foam, sandwiched between two brass shims in the form of an inner sole placed between the foot and the shoe is reported. Contact switching force decreases with module density, whilst position of the conductivity plugs in the footswitch is irrelevant. Comments on the construction of a footswitch using these modules are made, in particular no modification of the conductive rubber is needed and a density throughout greater than 4 modules per square inch leads to threshold switch forces of 30 N and less which is totally acceptable for gait analysis use without fears of contact being made whilst inserting and positioned in the subject's shoe.

Gait↗
PubMed1982

An experimental study of the use of a carbon fibre patch as a hernia prosthesis material.

Carbon fibre patches were inserted as prostheses into the dorsal lumbar fascia of rabbits. Their incorporation into the tissues was observed over a period of 15 weeks, and their mechanical properties were compared with those of implants made of a conventional Mersilene mesh. Although the mechanical properties of carbon fibre patches are initially poor, the development of a superior connective tissue response after several weeks suggests that a layered composite of carbon fibre and Mersilene with the latter giving initial strength may provide a useful material for clinical use as a hernia prosthesis.

Animals↗